The object of the present invention is to provide an apparatus for orienting patterns carried by masks, intended especially, but not exclusively, for the production by serigraphy of connector circuits of thick multiple layers, called multilayer circuits, and a device for performing the process.
The development of printed circuits is known to have resulted in the study of connection means for these circuits. Practically, such connection means have to consist of a large number of conductors, distributed over a very small surface with, certain conductors being, for example, 100 microns in width. One method of designing these connections consists of the application of multilayer circuits, in which the conductors are distributed over laminae, insulated one from the other, except at certain fixed points. The problem that is resolved by the present invention is that of the exact positioning of the conductors, one in relation to the other distributed over the various layers.
The manufacture of printed circuits of the multilayer type having thick layers is generally as follows: Each configuration desired is achieved by application, through a mask or screen, of a layer substance, which is either conductive or insulating, on an insulating substrate, which may be, for example, alumina. After each application of a layer, the substrate is removed from serigraphy apparatus and placed into a furnace at an elevated temperature (for example, on the order of 1,000.degree.) which depends, of course, on the type of substrate and layer. During this operation, the pasty layer solidifies, due to the removal of the solvents, and only a layer of metallic or insulating characteristics remains, strongly adhering to the substrate or to the preceding layer. The complete multilayer circuit is obtained by a series of such operations. It is absolutely essential that the position of the configurations, one in relation to the other, be very exact or else the connections between the layers would not be achieved.
By a known technique, the screens are stretched over a frame and coated with a photosensitive resin which is subjected to a partial insulation such that the resin is removed in certain places, thus forming a pattern for printing. The mask obtained in this manner is mounted on a serigraphy machine and the substrate, placed underneath the screen, receives the paste only through the transparent configuration of the screen. In a known device, the frame is inserted on two prongs which provide for its exact positioning in relation to the machine. Still, the photography does not permit one to accomplish a sufficiently exact positioning of the cliche (transparent configuration) in relation to the borders of the screen in the application, which is intended here, such that the adjustment, preceding the fabrication of the multilayer circuits, requires a good deal of time.
The superposition of different layers, therefore, involves a certain number of risks, which are intolerable in industrial production. It is the object of the present invention to remedy these shortcomings.